NATURE STUDY IN SCHOOLS. 131 



SYSTEMATIC ZOOLOGY FOR TEACHERS. 



BY 



C. J. Maynard. 



ORDER LOBOSA. 

 Amoebae. 



The minute animals which form this group of the root-footed animals 

 are often unprotected by shelly or other covering, but a large number of species 

 are provided with coverings which they secrete themselves, or which are made 

 of grains of sand, portions of diatoms or spicules. Amoebae live in both salt 

 and fresh water, also in damp earth. 



The common Protean amoeba may be taken as a type of this order. If 

 we remove the ooze from the surface of the mud in ditches, especially in 

 those where there is little or no current, and place it in a shallow dish for 

 a day or two, we shall quite likely discover that this species of amoeba is 

 present. A little of the water placed on the slide of a microscope, will prob- 

 ably show one or more of what are apparently minute drops of a jelly-like 

 substance. If these be closely examined for a time, they will be seen to 

 thrust out slender projections into one of which the remaining substance of 

 the body will frequently flow. This little drop of jelly or protoplasm is really 

 an amoeba, and the flowing process is its means of progression. These proc- 

 esses are known as pseudopodia or false feet. 



Form. When perfectly at rest, the amoeba has a spherical form, but 

 when moving and thrusting out its pseudopodia, it is so constantly changing 

 in form as to merit the name of proteus, which has been applied to it. This 

 change is accomplished very quickly, either by the body substance flowing 

 forward or by some of the pseudopodia being withdrawn. As a rule, how- 

 ever, the pseudopodia are more frequently thrust out in one direction than in 

 another, hence we may consider that the buds of the amoeba have an anterior 

 and a posterior end. 



Structure. When perfectly quiescent, the amoeba is seen to be sur- 

 rounded by an outer substance which appears to differ somewhat from the 

 inner- This outer substance, which may be considered to serve the purpose 

 of a kind of envelope or skin, thus maintaining the integrity of the amoeba 

 and preventing it from mingling with the surrounding water, is called the 

 ectoplasm. This clearly renders each amoeba a separate organism or indi- 

 vidual. Within this covering is a central substance, which appears to be 

 composed of course gravels, and which is known as the entoplasm. The 



